ENVIRONMENTAL IMPACT OF IRRIGATED AGRICULTURE IN UZBEKISTAN

Abstract

Land and water are the most important natural resources and are regarded as the permanent assets in- the service of mankind. It is important that these. resources must be used wisely so. that benefits from them are as far as possible, left undiminished for long periods.. Accordingly irrigation, drainage and reclamation projects must- be planned to achieve sustained high productive irrigated agricukure. `. In and and semi-arid regions,. irrigation provides the main; source of water for agriculture. But as the essence of successful irrigated agriculture ;`is'the maintenance of :favorable balance of moisture and salts, for plant growth in the soil. root zone, water table should not as a result of irrigation be permitted to rise and remain in the root-zone for :long periods and adversely affect agricultural production. Drainage is therefore an essential component of irrigation, which can remove excess irrigation water and salts for the root zone and thereby can create conditions favorable to plant growth. Irrigation plays, an important role in the economy-:of Uzbekistan. Owing : to the and climate of the region, crops must be irrigated in most. areas. Total--irrigato3 cropland is 4.274 Mha, which includes 1.624 Mha (38%) gram, 1495 Mha -'(35%) cotton, 256440 ha: (6%) orchard and. vineyards, 897540 ha. (21%) others. All Irrigation is full control irrigation, mainly using surface water. Main irrigation method is furrow irrigation. Pressurized irrigation systems only used in experiment fields and greenhouses. During_ 1970-1989 irrigated area expanded by factors of (150%) and (130%) in the Amudarya and Syrdarya river basin respectively. This required the diversion of ever-increasing quantities of water — Uzbekistan's annual intake of water grew from 35 km3 to 60-63 km in general water has been used inefficiently. In Uzbekistan, faimers withdraw an average of 14,000 m3 of water per hectare for irrigation, whereas rates in countries such as Egypt and Pakistan for efficient irrigation average around. 9000.10000 m3. Excessive emphasis on the extension of irrigation .systems- and construction of many medium and small-scale reservoirs have created problems for both the environment and system * efficiency; in particular substantial water losses - and . surplus of irrigation caused by implementation of misappropriate irrigation technologies, have led' to water i logging, soil: salinization, decline . of. water quality and also have resulted by the, aggravation of the Aral Sea status. Currently in Uzbekistan, -total agricultural area ill subjected to salinization is 3.722 Mha, out of which 1.080 Mha is the land of medium and highly salinized. The present salinization and water logging tendencies have been damaging crops and the yield is reducing rapidly. All the above-mentioned facts are consequence of using misappropriate irrigation practices in the country. In the dissertation entitled "Environmental Impact of Irrigated Agriculture in Uzbekistan" an attempt has been made to discuss main causes of waterlogging and salinization in the country. Irrigation practices of semi and and and countries reviewed withdraw lessons to Uzbekistan. Preventive/remedial measures such as surface drainage, subsurface drainage, mole drainage, physical and mechanical methods recommended to improve salt affected areas. CROPWAT software has been used to calculate crop water requirement for the main crops of the Country. Also Water and Salt Balance Model has been applied to cotton growing field of Syr-Darya region to simulate daily salt and water balance in the root zone.